Laurence Galoisy is a senior associate professor in Mineralogy at the Université Pierre et Marie Curie (Paris, France) where she conducts research at the Institute of Mineralogy, Material
Physics and Cosmo-chemistry (IMPMC). Her research focuses on structure-property relationships in minerals and glasses, using (micro) spectroscopic techniques (optical absorption spectroscopy
at high pressure and temperature, x-ray absorption spectroscopy), with interest on geochemical, industrial and archeological applications. She investigated the structural role of transitions
elements in glasses and minerals, and the relationship with glass coloration and the structural control of glass stability during alteration, with a special focus on nuclear glasses.

Institute of Mineralogy, Physics of Materials and Cosmochemistry, University Pierre and Marie Curie and CNRS, Paris, France

Since the discovery of glass making, the coloration caused by transition elements has always been one of the most attractive properties of glasses. Still now, transition metal ions constitute
the most important source of glass coloring agents. Coloration varies, for a given transition element, as a function of chemical and physical parameters such as glass composition or melting/fining
conditions. At the same time, the electronic transitions responsible for light selective absorption and glass coloration provide unique information about the local structure and chemical bonding of
glasses. This presentation aims to review optical absorption data at the light of complementary information provided by a broad range of experimental and numerical structural approaches, providing
a unique harvest of results: unusual coordination numbers as 5-fold coordination, distribution of site geometry, sensitivity to the chemical bond, medium-range organization, heterogeneous spatial
distribution… Some of these structural characteristics are inherited from the peculiar dynamics of silicate melts and may show a significant modification as a function of temperature. As transition
elements can be connected to the various structural subsets of glasses, they are useful color indicators of the complex structure of these materials. Vice versa, using a better knowledge of the
structural behavior of transition elements, the variation of colors may be rationalized as a function of glass composition and melting conditions.